1. Field of the Invention
This invention relates to a guide assembly, particularly for service in a nuclear reactor of the pressurized water type. The guide assembly functions as a flow restrictor for the primary water circuit passing through the reactor and as a guide for guiding a drive shaft connected to control rods.
2. Description of the Prior Art
In pressurized water reactors, for restricting (throttling) the flow of water in the primary circuit and for guiding the control rod drive shaft, a particular, dual-purpose guide assembly is used which is mounted in a top plate supported in a control rod guide tube in the zone of the reactor head plenum. Conventionally, the guide assembly comprise a grommet-like member which is fitted into a throughgoing aperture provided in the top plate. The grommet-like member is firmly held in the aperture by a plurality of flexure elements oriented parallel to the guide tube length and arranged circumferentially about the throughgoing aperture. The flexure elements are mounted in special fittings supported in the top plate.
The above-outlined conventional guide assembly requires machining and welding operations for installing the flexure members in the top plate and further, if the flexure elements need replacement, for example, because of stress corrosion, a time consuming assembly work is required which involves relatively long down times of the reactor.